According to the unconfirmed report, the boy seen was crying while sitting on a log off a remote track used by four-wheel-driving enthusiasts, about 20km south of the campsite where he was last seen.

Search crews raced to the location where the boy had been seen, but as the sun set there was still no sign of Luke.

Police speak to family members. Picture: Stuart Walmsley

Relatives have spent three tense days longing to be reunited with their "dear son".

More than 140 volunteers turned out to help find Luke, who has autism, after he went missing at 9.30am on Good Friday at the Devil Cove campground.

Senior Sergeant Ralph Willingham said Luke's parents, Tim and Rachel, had remained hopeful at Candlebark campground.

Sen-Sgt Willingham, himself a grandfather, fought back tears as he read their statement Sunday afternoon: "On this Easter Sunday we are grateful for everyone's compassion and caring. Thank you for the special effort and huge support in trying to locate our son. We just want our dear son Luke found."

Sen-Sgt Willingham said efforts would continue on the same scale today, if needed — the Easter long weekend being fortuitous in having people available to help.

"We're conducting a search for a missing person — that's our focus, but we are turning our mind to other circumstances that may have resulted in his disappearance," he said.

"There is nothing at all to indicate that we need to go down that line; we're ­considering everything we can think of, and our thoughts at this stage is that a young boy has wandered off from the campsite."

All campers in the area were registered but the records were not a priority given the effort was focused on search and rescue, he said.

Park rangers had been searching tents and vehicles, as Luke has a tendency to climb into them because he likes watching DVDs in the car.